1. Field of the Invention
The present invention relates to golf balls. More particularly, the present invention relates to a golf ball having a core, a cover and a paint layer.
2. Description of the Related Art
General golf balls have a core, a cover situated on the external side of this core, and a paint layer situated on the external side of this cover. The paint layer protects the cover and a mark layer. The paint layer is also responsible for aesthetic appearance of the golf ball. In addition, the paint layer is also responsible for antifouling property of the golf ball. Japanese Unexamined Patent Application Publication No. 2000-84116 (US 2001/003717) discloses a paint layer containing a polyurethane obtained by a reaction of an isocyanate with a certain polyol. This paint layer is excellent in adhesiveness with the cover. Japanese Unexamined Patent Application Publication No. 2000-230147 discloses a paint composition for golf balls containing a polyurethane having a specified viscosity. A layer obtained with this paint composition is excellent in adhesiveness with the cover.
Top concern to golf players for golf balls is their flight performances. The golf players particularly place great importance on travel distance attained by shots with a driver. The golf players also place great importance on travel distance on shots with a long iron and a middle iron.
Golf players place great importance also on spin performances of golf balls. Great back spin rate results in small run. For golf players, golf balls which are liable to be spun backwards are apt to be rendered to stop at a target position. Great side spin rate results in easily curved trajectory of the golf ball. For golf players, golf balls which are liable to be spun sidewise are apt to allow their trajectory to curve intentionally. The golf balls that are excellent in spin performances are excellent in control performances. High-level golf players particularly place great importance on control performances on shots with a short iron.
Japanese Unexamined Patent Application Publication No. 2004-8404 (US 2003/232665) discloses a golf ball provided with a cover having a Shore D hardness of 30 to 55. This cover is responsible for spin performances of the golf ball. Japanese Unexamined Patent Application Publication No. 2006-34740 (US 2006/025238) discloses a golf ball provided with a cover having a small volume. The base material of this cover is a polyurethane. This cover is responsible for spin performances of the golf ball. This cover does not impair the flight performances on shots with a driver.
When a golf ball placed on rough is hit, turfgrass will be interposed between the club face and the golf ball. Owing to this turfgrass, slipping of the golf ball occurs on the club face. A shot accompanied by slipping results in reduced spin rate. This phenomenon is referred to as a “flyer”. The flyer also occurs when water is interposed between the club face and the golf ball in case of rain.
When a flyer shot is made, the golf ball falls at a point farther than the point intended by the golf player. The flyer makes it difficult to predict the point of fall by the golf player. Golf balls that are likely to result in a flyer are inferior in control performances. Golf players expect golf balls less likely to result in a flyer. In other words, golf players expect golf balls that are superior in stability of the spin rate.
As described above, a soft cover can achieve excellent spin performances. However, a soft cover is greatly deformed upon shots. When a cover is deformed, the paint layer is also deformed following the deformation of the cover. When a cover is excessively deformed, a crack is generated on the paint layer. Abrasion of the paint layer from the cover may be also caused.
An object of the present invention is to provide a golf ball that is excellent in spin performances, stability of the spin rate and durability of the paint layer.